JP2022095616A - Package and packaging container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a package using a heat-shrinkable polyester film substantially not containing a non-crystalline component, or a packaging container having the same in at least part of an outer periphery of a container.

SOLUTION: A package, which is to be cut to fit a packaged object and in which an annular body with both ends of a film bonded together covers at least part of an outer periphery of a packaged object with thermal contraction, comprises, as a base material, a heat-shrinkable polyester film that (1) contains 90 mol% or more of an ethylene terephthalate unit in 100 mol% of a total ester unit, (2) has a melting peak in a temperature-rising process of a differential-scanning calorimeter (DSC), in which a melting point (Tm) that is a peak temperature thereof is 200°C or higher and 280°C or lower and a melting amount of heat (ΔHm) that is a peak area of the same is 40 J/g or greater and 60 J/g or smaller, and (3) in a circumferential direction of the packaged object, a peak of thermal shrinkage percentage appears at 60°C or higher and 120°C or lower, in which a thermal shrinkage percentage at the peak is 1% or greater and 40% or smaller.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a package after the heat-shrinkable polyester film is heat-shrinked and a packaging container on which the package is coated.

In recent years, in addition to applications such as label packaging, cap seals, and integrated packaging that protect glass bottles or plastic bottles and display products, polyvinyl chloride resin and polystyrene are also used for banding that binds containers such as lunch boxes. A stretched film made of a based resin or a polyester based resin (so-called heat-shrinkable film) is used. Among such heat-shrinkable films, polyvinyl chloride-based films have problems such as low heat resistance, generation of hydrogen chloride gas during incineration, and dioxin. In addition, polystyrene film is inferior in solvent resistance, it is necessary to use ink with a special composition at the time of printing, and it is necessary to incinerate it at a high temperature, and a large amount of black smoke is generated with an offensive odor at the time of incineration. There is a problem of doing. On the other hand, polyester-based heat-shrinkable films are widely used as heat-shrinkable labels because they have high heat resistance, are easy to incinerate, and have excellent solvent resistance, and are widely used as heat-shrinkable labels. As the amount increases, the amount used tends to increase more and more.
In recent years, there has been an active movement to reuse used PET bottles from the viewpoint of environmental problems and effective use of resources. For example, in the examples of Patent Document 1, a polyester-based film using 80% by weight of a PET resin (recycled PET) recycled from a PET bottle as a raw material is disclosed.

However, since the label using the film (recycled PET label) disclosed in Patent Document 1 does not have heat shrinkage performance and cannot be adhered to the bottle, the bottle used is limited to a part such as a barrel type. I came. That is, the recycled PET label has a problem that the design property and the applicable range are lower than those of the heat-shrinkable polyester-based film.

On the other hand, as the conventional heat-shrinkable polyester film, for example, as described in Patent Document 2, it is common to use an amorphous polyester raw material (amorphous raw material). This is because it is thought that amorphous molecules are involved in the development of shrinkage rate. For example, in the examples of Patent Document 2, it is shown that the shrinkage rate tends to increase as the content of the monomer as an amorphous component increases. However, the heat-shrinkable polyester-based film using an amorphous raw material cannot be recycled together because the composition of the resin is different from that of the PET bottle. This is because if a film made of an amorphous raw material is recycled together with a PET bottle, not only the composition of the recycled PET will change, but also the bottle crushed in the recycling process will be melted and solidified for regeneration. This is because the PET bottle and the label have different thermal characteristics, which causes an extrusion failure. The current recycling method requires a process of crushing used PET bottles together with labels, washing them with alkali, and then sorting using the difference in specific gravity between the bottles and labels (for example, by floating and sinking methods using water). Become. Furthermore, when a heat-shrinkable polyester film using an amorphous raw material is used as a label, there is a problem that the labels block each other when the content to be packaged is at a high temperature (for example, a hot beverage). rice field. Regarding this problem, for example, as described in Patent Document 3, a technique capable of preventing blocking by providing a blocking resistance improving layer on at least one side of a polyester-based base film is disclosed. However, even when the blocking-resistant layer is provided on the surface of the film, there is still a problem in recyclability. That is, since the blocking-resistant layer has a different composition from that of the container, it was also necessary to remove the label. Therefore, a label having both blocking resistance and recyclability is desired.

By the way, usually, when a heat-shrinkable film is used as a bottle label, the edges of the film are fixed to each other with a solvent, an adhesive or the like to form a ring-shaped (tube-shaped) label, which is then put on the bottle and shrunk. The method is adopted. By setting the shrinkage direction to the width direction, shrinkage labels can be continuously produced, which is efficient.
Therefore, Patent Document 4 discloses a heat-shrinkable film that heat-shrinks in the horizontal (width) direction and hardly heat-shrinks in the vertical (longitudinal) direction, and a method for producing the same. In the examples of Patent Document 4, polyethylene terephthalate is used as a raw material, and a film having a wrinkled treatment in the vertical direction is stretched horizontally and uniaxially to produce a film exhibiting desired heat shrinkage characteristics.

Further, the applicant of the present application has sufficient heat shrinkage characteristics in the main shrinkage direction, which is the longitudinal direction (mechanical direction), even if it does not contain a large amount of monomer components that can be amorphous components, and is orthogonal to the main shrinkage direction. Patent Document 5 discloses a heat-shrinkable polyester-based film having a low heat-shrinkability in the width direction (vertical direction) and a small thickness unevenness in the longitudinal direction. In Patent Document 5, a polyester-based unstretched film containing ethylene terephthalate as a main component and containing 0 mol% or more and 5 mol% or less of a monomer component which can be an amorphous component among all polyester resin components is used for lateral stretching. After that, the film is produced by a biaxial stretching method of longitudinal stretching. For example, as a stretching method A, a simultaneous biaxial stretching machine shown in FIG. 1 is used at a temperature of film Tg or more (Tg + 40 ° C.) or less. After stretching (transverse stretching) in the width direction at a magnification of 5 times or more and 6 times or less, the clip spacing is widened at a temperature of film Tg or more (Tg + 40 ° C.) to 1.5 times or more to 2.5 times or less. A method of relaxing in the width direction by narrowing the width of the tenter by 5% or more and 30% or less after the transverse stretching while stretching in the longitudinal direction (longitudinal stretching) at a magnification is described.

Japanese Patent No. 6150125 Japanese Unexamined Patent Publication No. 8-27260 Japanese Patent No. 5564753 Japanese Unexamined Patent Publication No. 5-169535 International Publication No. 2015/118968

Yuji Kumatani, "Fiber Structure Formation Mechanism and Development of High Performance Fibers", Journal of The Society of Fiber Science and Technology (Fibers and Industry), Vol. 63, No. 12 (2007) A. Mahendrasingam et al “Effect of draw ratio and temperature on the strain induced crystallization of poly (ethylene terephthalate) at fast draw rates” Polym. 40 5556 (1999)

As described above, the film of Patent Document 4 is disclosed as a heat-shrinkable film that shrinks significantly in the width direction. However, in the examples of Patent Document 4, the heat shrinkage rate at 95 ° C. in the width direction is 12.5% at the maximum, and it cannot be said that the shrinkage rate level required for the current heat shrinkage film is satisfied. ..

On the other hand, the heat-shrinkable polyester film described in Patent Document 5 has a main shrinkage direction in the longitudinal direction. Therefore, in the film whose main shrinkage direction is the width direction, a film having a high heat shrinkage rate in the width direction and a small thickness unevenness has not yet been disclosed. Even if the lateral → longitudinal stretching method described in Patent Document 5 is simply changed from longitudinal to transverse stretching, the non-shrinkage direction (longitudinal direction) cannot be relaxed and the shrinkage rate in the longitudinal direction becomes high, which is desired. No film is available. Further, even if the stretching is changed from vertical to horizontal, the thermal shrinkage stress in the width direction may increase.

The present invention has been made in view of the above circumstances, and an object thereof is a package or a package coated with an annular body using a heat-shrinkable polyester film containing substantially no amorphous component. It is an object of the present invention to provide a packaging container having at least a part of the outer periphery of the container, which has a high thermal shrinkage rate in the circumferential direction of the annular body, excellent appearance after shrinkage, and excellent heat-resistant blocking property, including PET bottles. It is an object of the present invention to provide a package coated with an annular body using a heat-shrinkable polyester-based film that can be recycled together with the container, or a packaging container having the same on at least a part of the outer periphery of the container.

The configuration of the present invention that solves the above problems is as follows.
1. 1. A package in which a heat-shrinkable polyester-based film is used as a base material and both ends of the film are bonded to each other in a heat-shrinked state on at least a part of the outer periphery of the object to be packaged. A package in which the annular body satisfies the following requirements (1) to (3).
(1) The heat-shrinkable polyester-based film used as the base material contains 90 mol% or more of the ethylene terephthalate unit in 100 mol% of all ester units. (2) The heat-shrinkable polyester-based film used as the base material performs differential scanning. It has a melting peak in the process of raising the temperature of the calorimeter (DSC), the melting point (Tm) which is the peak temperature is 200 ° C. or higher and 280 ° C. or lower, and the melting heat amount (ΔHm) which is the peak area is 40J. / G or more and 60 J / g or less (3) The peak of the heat shrinkage rate of the heat-shrinkable polyester-based film used as the base material obtained by thermal mechanical analysis (TMA) in the circumferential direction of the packaged object is 60 ° C or more and 120 ° C or less. The heat shrinkage at the peak is 1% or more and 40% or less. The package according to 1, wherein the peel strength of the adhesive portion of the coated annular body is 2N / 15 mm or more and 15N / 15 mm or less.
3. 3. The package according to 1 or 2, wherein the intrinsic viscosity (IV) of the heat-shrinkable polyester film as the base material is 0.5 dL / g or more and 0.8 dL / g or less.
4. 3. The package according to 1 to 3, wherein the adhesion is made by an organic solvent composition.
5. 4. The package according to 4, wherein the organic solvent composition contains a polymer component.
6. A packaging container comprising the package according to any one of 1 to 5 on at least a part of the outer circumference of the container.

According to the present invention, the heat-shrinkable polyester film is substantially free of amorphous components, has a high heat-shrinkability in the width direction (that is, the circumferential direction of the annular body), which is the main shrinkage direction of the heat-shrinkable polyester film, and has a high appearance after shrinkage. It is possible to provide a package coated with an annular body having excellent heat blocking properties. Therefore, the package can be recycled together with the container, which can contribute not only to the increase in recycling productivity but also to the improvement of the quality of recycled PET.

It is a heat shrinkage rate obtained from TMA for the packages of Example 1 and Comparative Example 1. It is a DSC curve of the heat-shrinkable polyester-based film which becomes the base material of the package of Example 1 and Comparative Example 3, and a PET bottle.

1. 1. Packaged body The packaged body of the present invention is formed by covering at least a part of the outer periphery of a packaged object with an annular body based on a heat-shrinkable polyester-based film and heat-shrinking the packaged object. Examples include PET bottles for beverages, various bottles, cans, plastic containers such as confectionery and lunch boxes, and paper boxes (hereinafter, these are collectively referred to as packaging objects). The package covered with the object to be packaged may or may not be printed, and is the circumference which is the main contraction direction of the annular body (hereinafter, may be referred to as a label). Perforations or notches may be provided in a direction orthogonal to the direction. Further, the label of the present invention may or may not be printed, but as an evaluation means thereof, in order to exclude the measurement disturbance element of the label print layer, only the film substrate without the label print layer is used. May be measured. That is, the unprinted label itself is a film base material, and the printed label may be evaluated as only a transparent film base material by wiping the printing layer with an organic solvent. .. This may be hereinafter referred to as "film substrate excluding the printing layer".
The thickness of the annular body (including the printed layer) of the present invention is preferably 5 μm or more and 200 μm or less, preferably 20 μm or more, considering that it is used for a label of a bottle, a banding film used for bundling a lunch box, or the like. 150 μm is more preferable. If the thickness exceeds 200 μm, the weight per area of the film simply increases, which is not economical. On the other hand, if the thickness is less than 5 μm, the film becomes extremely thin, which makes it difficult to handle (poor handleability) in a process such as forming an annular body.

1.1. Heat shrinkage rate of the package The annular body (film substrate excluding the printing layer) coated on the container of the present invention has a peak temperature of the heat shrinkage rate obtained by thermomechanical analysis (TMA) of 60 ° C. or higher and 120 ° C. or lower. It appears, and the heat shrinkage at the peak is preferably 1% or more and 40% or less. The heat shrinkage rate of the coated annular body means the heat shrinkage rate remaining after heat shrinkage of the heat shrinkable polyester film, which is a heat shrinkage polyester film, as described below. It can be rephrased as the heat shrinkage rate consumed when the container is heat-shrinked and coated. The fact that the peak temperature of the heat shrinkage rate of the coated annular body is higher than 120 ° C. indicates that the temperature at which the film is shrunk into the container is higher than the appropriate temperature, and the shrinkage finish is deteriorated. It will be easier. When the peak temperature of the heat shrinkage rate of the coated annular body is lower than 60 ° C., the film tends to shrink (dimension change) after being made into a package (even at room temperature), so that the design of the package is good. Not only is it likely to decrease, but it is also likely that the container will be deformed due to tightening, which is not preferable. The peak temperature of the heat shrinkage of the coated annular body is more preferably 65 ° C. or higher and 115 ° C. or lower, and further preferably 70 ° C. or higher and 120 ° C. or lower.

Further, when the heat shrinkage rate at the peak temperature of the coated annular body is higher than 40%, the consumption of the shrinkage rate becomes small when the coated annular body is heat-shrinked to the container, and the coated annular body is difficult to adhere to the container. turn into. If the adhesion to the container is small, the coated annular body tends to have poor appearance such as wrinkles and avatars, which is not preferable. On the other hand, if the heat shrinkage of the coated annular body is less than 1%, it means that the heat shrinkage of the film to the container is excessively developed, and the container is not only easily deformed but also coated. Vertical sink marks and wrinkles on the ring-shaped body (label) are likely to occur. In this case as well, poor appearance is likely to occur, which is not preferable. The heat shrinkage of the coated annular body is more preferably 2% or more and 35% or less.

1.2. Melting point (Tm), heat of fusion (ΔHm) of the coated annular body
The annular body (film substrate excluding the printing layer) coated on the container of the present invention is heated from 40 ° C. to 300 ° C. at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). The obtained thermogram has an endothermic peak (melting peak) that appears in a temperature range of 140 ° C. or higher, and the melting point (Tm), which is the peak temperature, is 200 ° C. or higher and 280 ° C. or lower, and the peak area thereof. It is preferable that a certain amount of heat of melting (ΔHm) is 40 J / g or more and 60 J / g or less. The Tm of the PET bottle is about 255 ° C. and the ΔHm is about 50 J / g when the temperature is raised from room temperature to 300 ° C. at a heating rate of 10 ° C./min by DSC. It is not preferable because problems are likely to occur when crushing, melting, solidifying and regenerating with a bottle. Specifically, when the Tm of the coated annular body is less than 200 ° C. or the ΔHm is less than 40 J / g, the resin adheres to the screw (so-called wrapping) when it is melted together with the PET bottle in the extrusion process. Problems such as are likely to occur. In addition, the above problem is likely to occur when the melting peak does not appear in the coated annular body. On the other hand, if the Tm of the package is higher than 280 ° C. or the ΔHm is higher than 60 J / g, the heat required for melting the coated annular body is insufficient when melting the package together with the PET bottle in the extrusion process. , There is a high possibility that the extrusion will stop due to a sudden increase in the extrusion pressure. The Tm of the coated annular body is more preferably 205 ° C. or higher and 275 ° C. or lower, and further preferably 210 ° C. or higher and 270 ° C. or lower. Further, the ΔHm of the coated annular body is more preferably 42 J / g or more and 58 J / g or less, and further preferably 44 J / g or more and 56 J / g or less.

1.3. Method of coating a container with an annular body 1.3.1. Method for forming an annular body In order to coat a packaged object with a heat-shrinkable polyester film, an annular body is formed in advance so that the main shrinkage direction is the circumferential direction, and then the annular body is covered with the packaged object. It is preferable to adopt a method of heat-shrinking. When forming an annular body, in addition to a method of adhering a heat-shrinkable polyester-based film using various adhesives, a method of fusing and adhering a heat-shrinkable polyester-based film using a high-temperature heating element. (For example, heat sealing method, impulse sealing method, fusing sealing method) and the like can also be used.
When forming an annular body using an adhesive, it is preferable to overlap and bond both ends of the heat-shrinkable polyester film. Here, the end portion means an end portion in the width direction (direction along the longitudinal direction), and is a position including a portion within 20 mm from the end portion. Conventionally, when forming an annular body from a heat-shrinkable film using an amorphous raw material, a solvent such as 1,3-dioxolane or tetrahydrofuran has been used as an adhesive solvent. However, as in the present invention, the heat-shrinkable polyester-based film containing more than 90 mol% of the ethylene terephthalate unit in all the ester units is difficult to dissolve with the solvent alone, so that it is difficult to obtain high adhesive strength. Further, although it is possible to adhere by using a hot melt in which a polyester resin is melted by heat as an adhesive, the film shrinks due to the heat of the hot melt and wrinkles are formed, so that an appearance defect is likely to occur. Further, since the hot melt has a high viscosity, it is difficult to stably apply a constant amount to the film in the step of applying the adhesive, and the higher the production speed, the lower the stability. Therefore, in the present invention, it is preferable to use an adhesive solvent composition in which a polymer composition is contained in a solvent (solvent) as an adhesive for forming an annular body, because the above-mentioned drawbacks can be covered.

Examples of the solvent used in the adhesive solvent composition include good solvents having high solubility in the polymer composition, and specific examples thereof include 1,3-dioxolane, tetrahydrofuran, toluene, 1,4-dioxane, 1,2. , 2,2-Tetrachloroethane, benzene, xylene and the like. Of these, 1,3-dioxolane and tetrahydrofuran are preferable because they have high solubility in the polymer composition, and among them, 1,3-dioxolane is particularly preferable because they have the highest solubility. Further, for the purpose of adjusting the adhesive strength of the annular body, a poor solvent having low solubility in the polymer composition may be mixed with the above-mentioned good solvent. Specific examples of the poor solvent include acetone, methyl ethyl ketone, ethyl acetate, butyl acetate, propyl acetate and the like. These good and poor solvents may be used in either a single state or a mixed state as long as the polymer composition can be dissolved.
The polymer composition used in the adhesive solvent composition is preferably polyester containing an ethylene terephthalate unit as a main component. Here, "having an ethylene terephthalate unit as a main component" means that the ethylene terephthalate unit is contained in an amount of 50 mol% or more with respect to the total amount of the components of the polyester. However, the ethylene terephthalate unit is preferably 70 mol% or less, preferably 60 mol% or less, based on 100 mol% of the polyester constituent unit, because the chemical resistance becomes stronger and the solubility in an organic solvent such as 1,3-dioxolane decreases. % Or less is more preferable. The ethylene terephthalate unit is preferably 5 mol% or more, more preferably 10 mol% or more, out of 100 mol% of the polyester constituent unit.

Examples of the dicarboxylic acid component other than terephthalic acid constituting the polyester used in the adhesive solvent composition include aromatic dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid and orthophthalic acid, adipic acid, azelaic acid, sebacic acid and decandicarboxylic acid. Such as aliphatic dicarboxylic acid, alicyclic dicarboxylic acid and the like can be mentioned.
Examples of the diol component other than ethylene glycol constituting the polyester used in the adhesive solvent composition include aliphatic diols such as 1,3-propanediol, 1,4-butanediol, neopentyl glycol, and hexanediol, 1,4. -Alicyclic diols such as cyclohexanedimethanol, aromatic diols such as bisphenol A and the like can be mentioned.
The polyester used in the adhesive solvent composition is an aromatic dicarboxylic acid such as isophthalic acid, an aliphatic dicarboxylic acid such as adipic acid, a cyclic diol such as 1,4-cyclohexanedimethanol, or a diol having 3 or more carbon atoms (for example,). A polyester containing at least one of (1,3-propanediol, 1,4-butanediol, neopentylglycol, hexanediol, etc.) and having a glass transition point (Tg) of 70 ° C. or lower is preferable.
Further, the polyester used in the adhesive solvent composition has a total of one or more monomer components that can be an amorphous component in 100 mol% of the polyvalent carboxylic acid component or 100 mol% of the polyvalent alcohol component in the total polyester resin. It is 30 mol% or more, preferably 40 mol% or more, and more preferably 50 mol% or more. This is because if the total of the monomer components that can be amorphous components is less than 30 mol%, the solubility in organic solvents such as 1,3-dioxolane is low and the solvent cannot be used as an adhesive solvent.

Examples of the monomer that can be an amorphous component include isophthalic acid, orthophthalic acid, adipic acid, sebacic acid, 1,4-cyclohexanedimethanol, neopentyl glycol, 1,3-propanediol, and 1,4-butanediol. Hexadiol can be mentioned.
The upper limit of the polyester content contained in the adhesive solvent composition is 25% by mass or less, preferably 20% by mass or less, and more preferably 15% by mass or less. This is because the higher the polyester content in the adhesive solvent composition, the higher the viscosity of the adhesive solvent composition, and in the process of adhering the edges of the film, the adhesive solvent composition is stably applied to the film in a constant amount. This is because it becomes difficult to apply. The lower limit of the polyester content contained in the adhesive solvent composition is 1% by mass or more, preferably 2% by weight or more. If the content of polyester contained in the adhesive solvent composition is less than 1% by mass, sufficient peel strength cannot be obtained when a polyester-based film containing more than 25% by mass of polyethylene terephthalate is adhered.
Various additives, thickeners, heat stabilizers, coloring pigments, anticoloring agents, ultraviolet absorbers and the like may be added to the adhesive solvent composition, if necessary.
Further, the lower limit of the viscosity of the adhesive solvent composition is not particularly limited, but if the viscosity is too low, it becomes difficult to stably apply a constant amount in the bonding step, so 100 mPa · s or less is preferable.

In the bonding step, it is preferable to apply the adhesive solvent composition to the film at about 50 to 550 mg / m2 using a known center seal machine or the like. Further, the coating width of the adhesive solvent composition in the adhesive step is preferably 1 mm or more in order to suppress peeling of the adhesive portion, and the upper limit is not particularly limited, but the smaller the label area used, the smaller the cost. It is preferably 10 mm or less.
The speed of the bonding step is not particularly limited, but is preferably 300 to 500 m / min in terms of speeding up. The annular body after the bonding step is usually folded flat and wound into a roll, and then the annular body is unwound and cut to a predetermined length to obtain a final product. However, in the case of making a final product, a cutting step may be performed without winding on a roll after the bonding step.

The coated annular body of the present invention preferably has a solvent-bonded portion having a peel strength of 2N / 15 mm or more, more preferably 3N / 15 mm or more, and particularly preferably 4N / 15 mm or more. When the peel strength is 2N / 15 mm or more, troubles such as peeling of the coated annular body from the container can be prevented. Further, in the coated annular body of the present invention, the upper limit of the peel strength of the solvent-bonded portion is less than 15 N / 15 mm. The higher the peel strength, the more preferable, but in the present invention, 15N / 15mm was the technical limit. The method for measuring the adhesive strength follows the method described in Examples.

When fusing and sealing a heat-shrinkable polyester film, a predetermined automatic bag making machine (for example, Kyoei Printing Machinery Materials Co., Ltd.-RP500) is used to set the temperature and angle of the fusing blade under predetermined conditions (for example, fusing). After adjusting the blade temperature to 240 ° C. and the blade angle to 70 ° C., a method of forming an annular body or a bag-shaped body at a predetermined speed (for example, 100 pieces / minute) can be adopted. In the present invention, the bag-shaped body is also included in the annular body. In addition, when the label is to be coated on the object to be packaged, a film constituting the annular body is wound around the object to be packaged and the overlapped portion is fused and sealed to form the annular body around the object to be packaged. It is also possible to adopt a method of heat-shrinking after covering.

1.3.2. Thermal shrinkage to the container A known method can be adopted to coat the container with the annular body produced above. That is, the container covered with the annular body before heat shrinkage is placed on a belt conveyor or the like, carried into the tunnel where the heat medium is blown out, and the annular body is heat-shrinked to cover the package. The method of covering the container with the annular body before heat shrinkage may be either manual or mechanical, and is not limited. Steam or hot air is used as the type of heat medium. The former is called a steam tunnel and the latter is called a hot air tunnel. As the heat medium, either steam or hot air may be used alone, or two types may be used by connecting these tunnels. Further, it is preferable that two or more zones having different temperature zones are connected to the tunnel because the finishability after shrinking the package into the container tends to be good. When a plurality of zones having different temperature zones are provided, it is a particularly preferable method to lower the temperature in the first zone and gradually increase the temperature in the subsequent zones because the finish quality is good. By heat-shrinking the label as it passes through these tunnels, the heat-shrinked annular body is coated on the container. The package of the present invention refers to a package after heat shrinkage.

The temperature inside the tunnel when the annular body is thermally shrunk is preferably 50 ° C. or higher and 120 ° C. or lower in the case of a steam tunnel, and 60 ° C. or higher and 230 ° C. or lower in the case of a hot air tunnel. If the temperature is lower than the lower limit temperature of each of the above, the maximum heat shrinkage stress in the width direction of the package tends to exceed 10 MPa, and poor appearance tends to occur, which is not preferable. When the temperature is higher than the upper limit temperature of each of the above, the maximum heat shrinkage stress in the width direction of the package tends to be less than 1 MPa, and the appearance defect is likely to occur, which is not preferable. In the case of a steam tunnel, it is more preferably 55 ° C. or higher and 115 ° C. or lower, and in the case of a hot air tunnel, it is more preferably 65 ° C. or higher and 225 ° C. or lower.
The residence time when passing through the tunnel is preferably 5 seconds or more and 60 seconds or less. If the residence time is 5 seconds or less, the heat shrinkage rate of the package tends to exceed 40%, and poor appearance tends to occur, which is not preferable. On the other hand, if the residence time is 60 seconds or less, the heat shrinkage rate of the package tends to be less than 1%, and the appearance is likely to be poor, which is not preferable. The residence time in the tunnel is more preferably 10 seconds or more and 55 seconds or less, and further preferably 15 seconds or more and 50 seconds or less.
Normally, when the container is coated with the annular body, the package is heat-shrinked by about 2 to 30% so as to be brought into close contact with the object to be packaged. The present invention also includes a packaging container having the label of the present invention on at least a part of the outer circumference of the container.

1.4. Intrinsic viscosity of package (IV)
The intrinsic viscosity (IV) of the annular body (film substrate excluding the printing layer) coated on the container of the present invention is preferably in the range of 0.5 to 0.8. If the IV of the annular body is lower than 0.5, the effect of improving the tear resistance is lowered and cracks are likely to occur during transportation, which is not preferable. On the other hand, if the IV is larger than 0.8, the filter pressure of the filter rises significantly when melt-extruding in the film forming process of the base film, which makes high-precision filtration difficult. The intrinsic viscosity is more preferably 0.52 or more and 0.78 or less.

2. 2. Polyester raw material used for heat-shrinkable polyester-based film The polyester raw material used for the heat-shrinkable polyester-based film of the present invention has an ethylene terephthalate unit in an amount of 90 mol% or more in 100 mol% of all ester units. It is preferably 95 mol% or more, and most preferably 100 mol%. The ethylene terephthalate unit contains ethylene glycol and terephthalic acid as main constituents. By using ethylene terephthalate, excellent heat resistance and transparency can be obtained as a heat-shrinkable polyester film, and the melting point Tm and the heat of fusion ΔHm can be brought close to those of a PET bottle.
The polyester raw material used in the present invention may contain an amorphous component (amorphous alcohol component and an amorphous acid component), but the ratio of the amorphous alcohol component to 100 mol% of the total alcohol component and the total acid component The total with the ratio of the amorphous acid component in 100 mol% is suppressed to 0 mol% or more and 5 mol% or less. When the amorphous component is contained in an amount of more than 5 mol%, there are problems that the melting peak is less likely to appear, the melting point Tm is likely to be less than 200 ° C., and the heat of fusion ΔHm is likely to be less than 40 J / g. These problems can be solved by setting the amorphous component to 5 mol% or less. In the present invention, as described above, it is preferable that the polyester is composed of only an ethylene terephthalate unit, but it is not positively copolymerized, and a constituent unit consisting of terephthalic acid and diethylene glycol is used as a by-product in the ethylene elephthalate unit. May exist. The smaller the content of the amorphous component, the better, and most preferably 0 mol%.

Examples of the monomer of the amorphous acid component (carboxylic acid component) include isophthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid and the like.
Examples of the monomer of the amorphous alcohol component (diol component) include neopentyl glycol, 1,4-cyclohexanedimethanol, diethylene glycol, 2,2-diethyl1,3-propanediol, and 2-n-butyl-2-. Examples thereof include ethyl-1,3-propanediol, 2,2-isopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, and hexanediol.
As the polyester raw material used in the present invention, 1,4-butanediol, which is a diol component other than ethylene glycol, may be used as a component other than the above-mentioned ethylene terephthalate and amorphous component. Although 1,4-butanediol lowers the melting point of the polyester film and is useful as a low Tg component, it is preferable that 1,4-butanediol is not contained as much as possible from the viewpoint of the present invention. By setting the content of 1,4-butanediol to 10 mol% or less, the melting point Tm and the heat of fusion ΔHm can be brought close to those of a PET bottle. The content of 1,4-butanediol in the total alcohol component and the total acid component is preferably 10 mol% or less, more preferably 5 mol% or less, and most preferably 0 mol%.

Various additives can be added to the polyester raw material used in the present invention, if necessary. The above additives are not particularly limited, and are known additives such as waxes, antioxidants, antistatic agents, crystal nucleating agents, thickeners, heat stabilizers, coloring pigments, anticoloring agents, and ultraviolet absorbers. Can be mentioned.
Further, in the polyester raw material, it is preferable to add fine particles acting as a lubricant in order to improve the workability (slipperiness) of the film. As the fine particles, any kind can be selected regardless of the types of the inorganic fine particles and the organic fine particles. Examples of the inorganic fine particles include silica, alumina, titanium dioxide, calcium carbonate, kaolin, barium sulfate and the like. Examples of the organic fine particles include acrylic resin particles, melamine resin particles, silicone resin particles, crosslinked polystyrene particles and the like. The average particle size of the fine particles is preferably in the range of about 0.05 to 3.0 μm when measured with a Coulter counter.
The method of blending the fine particles in the polyester raw material is not particularly limited, and for example, it can be added at any stage of producing a polyester resin, but it is subjected to polycondensation at the esterification stage or after the transesterification reaction is completed. It is preferable to add it as a slurry dispersed in ethylene glycol or the like at a stage before the start of the reaction to proceed with the polycondensation reaction. Further, a method of blending a slurry of fine particles dispersed in ethylene glycol or water using a kneaded extruder with a vent and a polyester resin raw material; or a method of blending the dried fine particles and a polyester resin raw material using a kneaded extruder. It may be done by a method of blending with and the like.

The intrinsic viscosity (IV) of the polyester raw material is preferably in the range of 0.5 to 0.8. If the IV is lower than 0.5, the effect of improving the tear resistance is lowered and cracks are likely to occur when the package is transported, which is not preferable. On the other hand, when IV is larger than 0.8, the increase in filtration pressure becomes large, which makes high-precision filtration difficult. The intrinsic viscosity is more preferably 0.52 or more and 0.78 or less.
The heat-shrinkable polyester-based film of the present invention can also be subjected to corona treatment, coating treatment, flame treatment, or the like in order to improve the printability and adhesiveness of the film surface.

3. 3. Characteristics of heat-shrinkable polyester-based film When the heat-shrinkable polyester-based film used for the annular body of the present invention is used for label applications of bottles, the most contributor to the shrinkage finish of the label is 90 ° C. in the width direction and the longitudinal length. The temperature is 70 ° C. and 90 ° C. in the direction, and it is technically more difficult to control the shrinkage rate in the temperature zone than in other temperature zones. According to the present invention, a heat-shrinkable polyester-based film having a very high heat-shrinkage rate in the width direction, which is the main shrinkage direction, and a low heat-shrinkage rate in the longitudinal direction, and having a small thickness unevenness is formed into an annular body. It is very useful in that it can be used as.
3.1 Heat shrinkage in the width direction The heat-shrinkable polyester film used for the annular body of the present invention has a shrinkage rate of 50% in the width direction (main shrinkage direction) when immersed in hot water at 90 ° C. for 10 seconds. It is preferably 75% or more and preferably 75% or less. Here, the "width direction" is a direction orthogonal to the longitudinal direction (machine direction; MD), and is also called a transverse direction (TD). If the heat shrinkage rate in the width direction at 90 ° C. is less than 50%, the film shrinks insufficiently when the container or the like is coated and shrunk, and the film does not adhere to the container cleanly, resulting in poor appearance, which is not preferable. On the other hand, if the heat shrinkage rate in the width direction at 90 ° C. exceeds 75%, the shrinkage rate becomes extremely high when the container or the like is coated and shrunk, and the film is distorted, which is not preferable. The heat shrinkage rate in the width direction at 90 ° C. is more preferably 55% or more and 70% or less, and further preferably 60% or more and 65% or less.

3.2. Thermal shrinkage in the longitudinal direction The heat-shrinkable polyester film used for the annular body of the present invention has a thermal shrinkage of -6% in the longitudinal direction (mechanical direction, MD) when immersed in hot water at 90 ° C. for 10 seconds. It is preferably 14% or more and preferably 14% or less. If the heat shrinkage rate in the longitudinal direction at 90 ° C. is less than -6%, it is not preferable because when the container or the like is coated and shrunk, it is easily stretched and wrinkled easily, and a good shrinkage appearance cannot be obtained. On the other hand, if the heat shrinkage rate in the longitudinal direction at 90 ° C. exceeds 14%, distortion and sink marks are likely to occur after shrinkage, which is not preferable. The heat shrinkage rate in the longitudinal direction at 90 ° C. is more preferably -4% or more and 12% or less, and further preferably -2% or more and 10% or less.
Further, the heat-shrinkable polyester film used for the annular body of the present invention has a heat-shrinkage rate of -6% or more and 6% or less in the longitudinal direction (mechanical direction, MD) when immersed in hot water at 70 ° C. for 10 seconds. It is preferable to have it. If the heat shrinkage rate in the longitudinal direction at 70 ° C. is less than -6%, it is not preferable because when the container or the like is coated and shrunk, it is likely to be stretched too much and wrinkle easily, and a good shrinkage appearance cannot be obtained. On the other hand, if the heat shrinkage rate in the longitudinal direction at 70 ° C. exceeds 6%, distortion and sink marks are likely to occur after shrinkage, which is not preferable. The heat shrinkage rate in the longitudinal direction at 70 ° C. is more preferably -4% or more and 4% or less, and further preferably -2% or more and 2% or less.

3.3. Thickness unevenness in the width direction The heat-shrinkable polyester film used for the annular body of the present invention preferably has a thickness unevenness of 1% or more and 20% or less when the measured length is 1 m in the width direction. If the thickness unevenness in the width direction exceeds 20%, not only appearance defects such as end face misalignment and wrinkles occur when the film is wound as a roll, but also printing defects are likely to occur when printing the film, which is preferable. do not have. The thickness unevenness in the longitudinal direction is more preferably 19% or less, further preferably 18% or less. The smaller the thickness unevenness in the width direction is, the more preferable it is, but considering the performance of the film forming apparatus and the like, it is considered that the limit is about 1%.

3.4. Maximum heat shrinkage stress in the width direction The heat shrinkable polyester film used for the annular body of the present invention has a maximum heat shrinkage stress in the shrinkage direction obtained by mechanical analysis (TMA) of 4 MPa or more and 13 MPa or less before heat shrinkage. Is preferable.
If the maximum heat shrinkage stress in the width direction exceeds 13 MPa during heat shrinkage, the object to be packaged such as a container is likely to be deformed, which is not preferable. On the other hand, if the maximum heat shrinkage stress in the width direction is less than 4 MPa, the degree of adhesion to the container during heat shrinkage decreases, and the finish after shrinkage deteriorates, which is not preferable. The maximum heat shrinkage stress in the width direction before heat shrinkage is more preferably 5 MPa or more and 12 MPa or less, and further preferably 6 MPa or more and 11 MPa or less.

3.5. Crystallinity Calculated from Density The heat-shrinkable polyester film used for the annular body of the present invention preferably has a crystallinity calculated from the density of 1% or more and 15% or less. When the degree of crystallinity exceeds 15%, the heat shrinkage rate in the width direction increases. The relationship between the heat shrinkage rate and the crystallinity in the width direction will be described later. The lower the crystallinity, the more the heat shrinkage rate in the width direction increases, which is better, more preferably 13% or less, still more preferably 11% or less. The lower limit of the crystallinity is about 1% at the current state of the art. The method for measuring the crystallinity is described in the column of Examples.

3.6. Other properties The thickness of the heat-shrinkable polyester film (film base material excluding the printing layer) used for the annular body in the present invention is used for label applications of bottles and banding film applications used for binding purposes such as lunch boxes. It is preferably 5 μm or more and 200 μm or less, and more preferably 20 μm or more and 150 μm or less. If the thickness exceeds 200 μm, the weight per area of the film simply increases, which is not economical. On the other hand, if the thickness is less than 5 μm, the film becomes extremely thin, which makes it difficult to handle (poor handling) in a process such as forming an annular body.
The haze value is preferably 2% or more and 13% or less. If the haze value exceeds 13%, the transparency becomes poor and the appearance may be deteriorated when creating a label, which is not preferable. The haze value is more preferably 11% or less, further preferably 9% or less. The smaller the haze value is, the more preferable it is, but considering that a predetermined amount of lubricant must be added to the film for the purpose of imparting slipperiness necessary for practical use, the lower limit is about 2%.

4. Method for producing a heat-shrinkable polyester-based film used for an annular body The heat-shrinkable polyester-based film used for the ring-shaped body of the present invention is described in 2. above. It can be produced by laterally stretching under the following conditions using an unstretched film obtained by melt-extruding the raw material described in the polyester raw material used for the heat-shrinkable polyester-based film with an extruder. Specifically, the preheated film is preheated at a temperature (T1) of (Tg + 40 ° C.) or higher (Tg + 70 ° C.) or lower, and the preheated film is transversely stretched at a temperature (T2) of (Tg + 5 ° C.) or higher (Tg + 40 ° C.) or lower. The laterally stretched film is further stretched at a temperature (T3) of (Tg-10 ° C.) or higher (Tg + 15 ° C.) or lower. Here, the T1, T2, and T3 satisfy the relationship of T1>T2> T3. If necessary, after the second transverse stretching at T3, heat treatment may be performed at a temperature of (Tg-30 ° C.) or more and Tg or less. The polyester can be obtained by polycondensing the above-mentioned suitable dicarboxylic acid component and diol component by a known method. Usually, two or more kinds of chip-shaped polyester are mixed and used as a raw material for a film.
Hereinafter, each step will be described in detail.

4.1. When the raw material resin is melt-extruded, it is preferable to dry the polyester raw material using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer. After the polyester raw material is dried in this way, it is melted at a temperature of 200 to 300 ° C. using an extruder and extruded into a film. For extrusion, any existing method such as the T-die method and the tubular method can be adopted.
Then, an unstretched film can be obtained by quenching the sheet-shaped molten resin after extrusion. As a method for rapidly cooling the molten resin, a method of casting the molten resin from a base onto a rotary drum and quenching and solidifying the molten resin to obtain a substantially unoriented resin sheet is preferably used.
By stretching the obtained unstretched film in the width (lateral) direction by the method described in detail below, a heat-shrinkable polyester-based film used for the annular body of the present invention can be obtained.

4.2. Lateral Stretching Hereinafter, regarding the stretching method for obtaining the heat-shrinkable polyester-based film used for the annular body of the present invention, the conventional method for forming a heat-shrinkable polyester-based film and the molecules with reference to Non-Patent Documents 1 and 2. It will be explained in detail while considering the difference from the structure.
The details of the molecular structure that governs the shrinkage behavior of the film have not been clarified yet, but it is roughly considered that the oriented amorphous molecules are involved in the shrinkage characteristics. Therefore, the heat-shrinkable polyester film is usually produced by using an amorphous raw material and stretching it in a direction to be shrunk (main shrinkage direction, usually width direction). A heat-shrinkable polyester film using a conventional amorphous raw material generally has a stretching ratio (final stretching) of about 3.5 to 5.5 times at a temperature from the glass transition temperature (Tg) to Tg + 30 ° C. It is manufactured by stretching at (magnification). It is considered that the amorphous molecules are oriented by these stretching conditions and the film has a shrinkage rate. The lower the stretching temperature or the higher the stretching ratio, the higher the shrinkage rate (that is, the amorphous molecules are oriented). It will be easier).
On the other hand, like the heat-shrinkable polyester film used for the annular body of the present invention, the monomer component (amorphous raw material) that can be an amorphous component is 0 mol% or more and 5 mol% or less, which is a substantially amorphous raw material. When the film is stretched at the same temperature as above, that is, at a temperature of Tg to Tg + 30 ° C., the film shrinks when stretched at a magnification of 2 to 2.5 times, but the same magnification as above, that is, 3.5. If the film is stretched about 2 to 5.5 times, the shrinkage rate of the film will decrease. For example, Comparative Examples 1 and 3 in Table 1 described later are all 3.6 at a temperature of 85 to 90 ° C. (Comparative Example 1) or 80 ° C. (Comparative Example 3) using a polyester raw material having Tg = 75 ° C. This is an example in which a film was produced by laterally stretching the film by a factor of 2 (Comparative Example 1) or 2.4 times (Comparative Example 3). In Comparative Example 3 in which the draw ratio is as low as 2.4 times, the shrinkage ratio in the width direction is as high as 55.3%, but in Comparative Example 1 in which the draw ratio is as high as 3.6 times, the shrinkage ratio in the width direction is 26.8%. It dropped significantly.

It is considered that the reason for this is that the molecules oriented by stretching crystallize (aligned crystallization) and inhibit the shrinkage of the film (that is, the shrinkage of the amorphous molecule). For example, FIG. 4 of Non-Patent Document 1 shows the relationship between stress (horizontal axis) and birefringence (vertical axis) in uniaxial stretching of polyethylene terephthalate fiber, and the state of change in molecular orientation can be read from this figure. be able to. That is, in the region where the stretching ratio DR is up to about 2 times, the stress and the birefringence have a linear relationship, and when the stretching is stopped, the stress is relaxed and the birefringence decreases. The decrease in birefringence indicates relaxation of the molecular chain, and when replaced with a film, it is considered to indicate shrinkage of the film (expression of shrinkage rate). On the other hand, when the draw ratio DR exceeds 2 times, it becomes difficult to establish a linear relationship between stress and birefringence, and even if stretching is stopped, no decrease in birefringence can be seen. It is considered that this phenomenon indicates a decrease in the shrinkage rate due to orientation crystallization. From this, it is considered that the shrinkage ratio can be developed in the film under the condition that the orientation crystallization due to stretching does not occur even when the amorphous raw material is not substantially contained as in the present invention. ..

Here, the stretching condition in which the orientation does not crystallize even when stretched is shown in, for example, the photograph of FIG. 2 of Non-Patent Document 2. Here, a crystal peak was observed at low temperature stretching at 85 ° C (= Tg + 10 ° C), whereas no crystal peak was observed at high temperature stretching at about 130 ° C (= Tg + 55 ° C), and the molecule was completely oriented and crystallized. It is shown not to. It is believed that this is because in high temperature stretching, the relaxation of molecules that occurs during stretching is faster than the orientation rate. As a matter of fact, when the present inventors carried out high-temperature stretching at a constant temperature of 130 ° C. on the film production line, the shrinkage rate did not develop because the molecules were not oriented according to the above mechanism. Furthermore, it was found that not only the shrinkage rate was not observed, but also the thickness unevenness was poor (increased) because the stress during stretching did not increase.
Therefore, the present inventors do not perform the entire stretching process as high-temperature stretching (constant) as described above, but instead use a step of hardly orienting the molecules by high-temperature stretching and a step of positively orienting the molecules by low-temperature stretching. To complete the present invention, it was found that the shrinkage rate can be expressed by orienting only amorphous molecules while suppressing the decrease in the shrinkage rate due to the orientation crystallization, and the thickness unevenness can be suppressed to a low level. I arrived. Specifically, as described in detail below, only amorphous molecules are put into the film by a method of preheating at temperature T1, laterally stretching at temperature T2, and then transversely stretching at temperature T3 (T1>T2> T3). It was found that the temperature can be controlled in the longitudinal direction and the thermal shrinkage in the width direction, and that the thickness unevenness in the width direction can be reduced.

Hereinafter, each step will be described in sequence.
First, the preheating zone is preheated at a temperature T1 of (Tg + 40 ° C.) or higher (Tg + 70 ° C.) or lower. If the preheating temperature T1 is less than (Tg + 40 ° C.), the molecules tend to be oriented and crystallized during the transverse stretching in T2 in the next step, and the heat shrinkage in the film width direction tends to fall below the lower limit of 50% (described later). See Comparative Example 1 in Table 1). Further, when the preheating temperature T1 is (Tg + 40 ° C. or less), the stress applied in the vertical direction due to the neck-in generated by the lateral stretching increases, and the heat shrinkage rate in the longitudinal direction tends to exceed the upper limit of 6%, which is not preferable. On the other hand, if the preheating temperature T1 exceeds (Tg + 70 ° C.), the thickness unevenness in the width direction worsens and easily exceeds the upper limit of 20%, which is not preferable. The preheating temperature T1 is more preferably (Tg + 45 ° C.) or higher (Tg + 65 ° C.) or lower, and further preferably (Tg + 50 ° C.) or higher (Tg + 60 ° C.) or lower.
Specifically, it is preferable to control the passage time of the preheating zone to 2 seconds or more and 10 seconds or less so that the preheating temperature is T1. If the passing time of the preheating zone is less than 2 seconds, the lateral stretching at T2 in the next step is started before the film reaches the preheating temperature T1. Therefore, the same problem as when the preheating temperature T1 is less than (Tg + 40 ° C.) occurs. The longer the passing time of the preheating zone, the easier it is for the film temperature to reach the preheating temperature T1, which is preferable. However, if the passing time is too long, the temperature of the preheating zone is set to exceed the cold crystallization temperature. It is not preferable because the crystallization of the unstretched film is excessively promoted. Further, the longer the passage time of the preheating zone, the larger the production equipment, which is not preferable. A passing time of the preheating zone of 10 seconds is sufficient.

Next, the film preheated at the temperature T1 is transversely stretched at a temperature T2 of (Tg + 5 ° C.) or higher (Tg + 40 ° C.) (sometimes referred to as first transverse stretching). In the first transverse stretching, it is necessary to suppress the molecular orientation due to stretching as described above, and the temperature T2 in the first transverse stretching is set lower than the preheating temperature T1 to be (Tg + 5 ° C) or higher (Tg + 40 ° C) or lower. Control. If the temperature T2 in the first transverse stretching is less than (Tg + 5 ° C.), the same problem as in the preheating occurs, and not only the heat shrinkage in the film width direction tends to fall below the lower limit of 50%, but also in the longitudinal direction. It is not preferable because the heat shrinkage rate tends to exceed the upper limit of 6%. On the other hand, if the temperature T2 in the first transverse stretching exceeds (Tg + 40 ° C.), the thickness unevenness in the width direction tends to exceed the upper limit of 20%, which is not preferable. The temperature T2 in the first transverse stretching is more preferably (Tg + 10 ° C.) or higher (Tg + 35 ° C.) or lower, and further preferably (Tg + 15 ° C.) or higher (Tg + 30 ° C.) or lower.
Further, the draw ratio in the first transverse stretching is preferably 1.5 times or more and 2.5 times or less. When the draw ratio in the first transverse stretching is less than 1.5 times, the effect of suppressing the orientation crystallization becomes small, the shrinkage in the film width direction tends to be less than 50%, and the shrinkage in the longitudinal direction is 6. It is not preferable because it easily exceeds%. On the other hand, if the stretching ratio in the first transverse stretching exceeds 5 times, the thickness unevenness in the width direction tends to exceed 20%, which is not preferable. The draw ratio in the first transverse stretching is more preferably 1.6 times or more and 2.4 times or less, and further preferably 1.7 times or more and 2.3 times or less.

The laterally stretched film is further stretched at a temperature T3 of (Tg-10 ° C.) or higher (Tg + 15 ° C.) or lower (sometimes referred to as second transverse stretching). As described above, in the first transverse stretching, the molecule is stretched at a high temperature so that the molecular orientation is suppressed, but in the subsequent second transverse stretching, on the contrary, it is necessary to positively cause the molecular orientation by stretching. Therefore, in the present invention, the product is stretched at a low temperature so that T2> T3, and specifically, the temperature T3 in the second transverse stretching is (Tg-10 ° C.) or higher (Tg + 15 ° C. or lower). When the temperature T3 in the second transverse stretching is lower than (Tg-10 ° C.), the stress applied in the longitudinal direction due to the neck-in generated in the transverse stretching increases, and the heat shrinkage in the longitudinal direction tends to exceed the upper limit of 6%. It is not preferable because it will end up. On the other hand, when the temperature T3 in the second transverse stretching exceeds (Tg + 15 ° C.), the molecular orientation becomes small and the heat shrinkage in the width direction tends to fall below the lower limit of 50% (comparative example in Table 1 described later). See 5). The temperature T3 in the second transverse stretching is more preferably (Tg-7 ° C.) or higher (Tg + 12 ° C.) or lower, and further preferably (Tg-4 ° C.) or higher (Tg + 9 ° C.) or lower.

Further, the draw ratio in the second transverse stretching is preferably 1.5 times or more and 2.5 times or less. If the stretching ratio in the second transverse stretching is less than 1.5 times, the thickness unevenness in the width direction is deteriorated. On the other hand, when the draw ratio exceeds 2.5 times in the second transverse stretching, not only the shrinkage rate in the width direction tends to decrease, but also the shrinkage stress in the width direction increases. The draw ratio in the second transverse stretching is more preferably 1.6 times or more and 2.4 times or less, and further preferably 1.7 times or more and 2.3 times or less.
The final draw ratio (the product of the draw ratio in the first transverse stretch and the draw ratio in the second transverse stretch) is preferably 3 times or more and 5.5 times or less. If the final draw ratio is less than 3 times, not only the shrinkage rate in the width direction tends to decrease, but also the thickness unevenness in the width direction worsens. On the other hand, when the final draw ratio exceeds 5.5 times, breakage is likely to occur during stretching in the width direction. The final draw ratio is more preferably 3.1 times or more and 5.4 times or less, and further preferably 3.2 times or more and 5.3 times or less.
In the heat-shrinkable polyester-based film used for the annular body of the present invention, the preheating temperature T1, the temperature T2 in the first stretching, and the temperature T3 in the second stretching satisfy the relationship of T1>T2> T3. A desired film can be obtained by laterally stretching so that the individual T1, T2, and T3 satisfy the above range while satisfying this relationship.

4.3. Heat treatment The film subjected to the transverse stretching as described above may be heat-treated in a state where both ends in the width direction are gripped by clips in the tenter, if necessary. Here, the heat treatment means heat treatment at a temperature of (Tg-20 ° C.) or more and Tg or less for 1 second or more and 9 seconds or less. Such heat treatment is preferably used because it can suppress a decrease in heat shrinkage and improve dimensional stability after storage over time. If the heat treatment temperature is lower than (Tg-20 ° C.), the above effect of the heat treatment is not effectively exhibited. On the other hand, when the heat treatment temperature is higher than Tg, the heat shrinkage rate in the width direction tends to fall below the lower limit of 50%.
The temperature during the heat treatment is preferably not less than the temperature T3 in the second stretching.
Based on the above heat treatment regulations, all of Examples 1 to 6 and Comparative Examples 1 to 3 and 5 (all Tg = 75 ° C.) described later have a heating temperature of 50 after transverse stretching, except for Example 2. Since it is ° C. and does not satisfy the above temperature range, it is not regarded as an example of performing the heat treatment in the present invention. On the other hand, in Example 2, since the heating temperature after lateral stretching was 75 ° C., it is regarded as an example of performing the heat treatment in the present invention.
The longer the heat treatment time, the easier it is to exert the effect, but if it is too long, the equipment becomes huge, so it is preferable to control it to 1 second or more and 9 seconds or less. More preferably, it is 5 seconds or more and 8 seconds or less.
Further, in the heat treatment step, relaxation in the width direction can be performed by reducing the distance between the gripping clips in the tenter. This makes it possible to suppress dimensional changes and deterioration of heat shrinkage characteristics after storage over time.

Next, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the aspects of these Examples and may be modified without departing from the spirit of the present invention. It is possible.

[Polyester synthesis]
Terephthalic acid (TPA), isophthalic acid (IPA) as acid components in a stainless steel autoclave equipped with a stirrer, thermometer and partial recirculation cooler so that the resin composition after polymerization has the composition shown in Table 1. , Sebacic acid (SA), adipic acid (AA), ethylene glycol (EG), neopentyl glycol (NPG), 1,4-cyclohexanedimethanol (CHDM), butanediol (BD) as glycol components, respectively. The esterification reaction was carried out from 140 ° C. to 220 ° C. for 4 hours while removing the accumulated water from the system. Then, the pressure was gradually reduced to 133.3 Pa over 60 minutes and the temperature was raised to 270 ° C. Further, a polycondensation reaction was carried out at 270 ° C. for about 90 minutes under a reduced pressure of 13.3 to 40.0 Pa to obtain copolymerized polyesters A to C. The resin compositions of the obtained copolymerized polyesters A to G are shown in Table 1. The DEG in Table 1 is diethylene glycol, which is a by-product produced by polymerization. In Table 1, the content of each monomer component in 100 mol% of the total acid component is in the column of "acid component", and the content of each monomer component in 100 mol% of the total polyhydric alcohol component is in the column of "polyhydric alcohol component". It shows the content of the monomer component.

[Manufacturing method of film 1]
Polyester D and polyester E were mixed at a mass ratio of 95: 5 and charged into an extruder. This mixed resin was melted at 280 ° C., extruded from a T-die, wound around a rotating metal roll cooled to a surface temperature of 30 ° C., and rapidly cooled to obtain an unstretched film having a thickness of about 150 μm. The Tg of the unstretched film was 75 ° C.
The obtained unstretched film was guided to a transverse stretching machine (tenter) and preheated at 135 ° C. for 5 seconds. The preheated film was continuously led to the first half zone of lateral stretching and laterally stretched at 105 ° C. until it became 2.1 times. Subsequently, in the latter half zone of lateral stretching, lateral stretching was performed at 81 ° C. until the temperature increased 1.9 times. The final lateral stretch ratio was 4.0 times. Finally, after heat-treating at 50 ° C. for 3 seconds in the heat treatment zone, the film is cooled, both edges are cut and removed, and the film is wound into a roll with a width of about 242 mm to obtain a transversely stretched film having a thickness of 40 μm. It was manufactured continuously over a length to give film 1. Table 2 shows the manufacturing conditions and characteristics of the film 1.

[Manufacturing method of films 2 to 6]
The films 2 to 6 were evaluated by forming a film by the same manufacturing method as that of the film 1 except that the polyester raw material and the transverse stretching conditions were changed. Table 2 shows the manufacturing conditions and characteristics of each film.
As for the film 6, since the method for calculating the crystallinity by the above formula 3 cannot be applied, the column of Table 2 is described as “−”.

[Shrinkage finish]
From the roll on which the above heat-shrinkable label is wound, a heat-shrinkable label cut at a pitch of 90 mm in the longitudinal direction is collected, placed on a commercially available 280 ml PET bottle (Oi Ocha manufactured by ITO EN, containing contents, unopened), and Fuji. A steam tunnel manufactured by Astec Inc (model; SH-1500-L) was used and heat-shrinked through steam (tunnel conditions are described in Examples or Comparative Examples).
The finishability of the label after shrinkage was visually evaluated on a 5-point scale according to the following criteria. The defects described below mean jumping up, wrinkles, insufficient shrinkage, folds at the end of the label, shrinkage whitening, fading of printing ink, and the like.
5: Best finish (no defects)
4: Good finish (with one defect)
3: There are 2 defects 2: There are 3 to 5 defects 1: There are many defects (6 or more)

[Heat shrinkage rate (after heat shrinkage)]
A sample of 4 mm in the longitudinal direction × 25 mm in the width direction (circumferential direction of the bottle) was cut out from the label for which the shrinkage finish was evaluated, and the heat shrinkage rate was measured in the displacement mode using TMA SS100 manufactured by Seiko Electronics Co., Ltd. The distance between the chucks is 15 mm, the sample is attached to the probe using a dedicated chuck so that the direction between the chucks is the width direction of the label, and the temperature rises from 30 ° C to 130 ° C at 10 ° C / min with a load of 49 mN. It was warm. From the obtained displacement, the heat shrinkage rate was obtained according to the following equation 1.
Heat shrinkage rate (%) = {(length before shrinkage-length after shrinkage) / length before shrinkage} × 100 Equation 1

[Resin composition of base film]
10 mg of the base film from which the printed layer was removed from the package was dissolved in 0.6 ml of a solvent in which deuterated chloroform / trifluoroacetic acid was mixed at a volume ratio of 85% / 15%, and a nuclear magnetic resonance spectrometer (NMR) manufactured by Varian Co., Ltd. was dissolved. ) 1H-NMR analysis was performed using Gemini-200 (500 MHz) with 32 integrations. For the obtained NMR spectrum, the molar% ratio of the resin was determined from the integral ratio using the analysis software JEOL RESONANCE (manufactured by JEOL Ltd.).
[Melting point (Tm), heat of fusion (ΔHm)]
Using a differential scanning calorimeter (model: DSC220) manufactured by Seiko Electronics Inc., the melting point Tm and the calorific value of melting ΔHm were determined according to JIS-K7121-1987. Specifically, 10 mg of the base film from which the printed layer was removed from the package was heated from 30 ° C. to 300 ° C. at a heating rate of 10 ° C./min, and the endothermic curve was measured. The peak temperature appearing at 140 ° C. or higher of the obtained endothermic curve was defined as the melting point Tm (° C.), and the peak area was defined as the heat of fusion ΔHm (J / g). When two or more endothermic peaks appeared, the peak with a higher temperature was defined as Tm, and ΔHm was obtained from the peak.

[Heat blocking property]
After filling the labeled bottle with water and closing the lid, which was used for the evaluation of the shrinkage finish described above, the label was placed in a constant temperature bath (LHU-124 manufactured by Espec) adjusted to 60 ° C./50% RH. Ten pieces were put in contact with each other and left for one week. After that, the bottles with labels were taken out, and the heat-resistant blocking property was evaluated as ◯ if the labels were not blocking each other and × if they were blocking.

[Recyclability]
After crushing 500 bottles with labels used for the above evaluation of shrinkage finish to obtain flakes, a 3.5% by weight sodium hydroxide solution under the conditions of a flake concentration of 10% by weight, 85 ° C. and 30 minutes. Was washed with stirring. After the alkaline washing, the flakes were taken out and washed with distilled water under the conditions of a flake concentration of 10% by weight, 25 ° C. and 20 minutes under stirring. This washing with water was repeated twice more by exchanging distilled water. After the flakes washed with water are dried, they are melted by an extruder, and the filter is changed to a finer one with an opening size in sequence, and finer foreign matter is filtered out twice, and the third time with the smallest opening size filter of 50 μm. By filtration, recycled polyester was obtained. In addition, recycled polyester was obtained in the same manner for PET bottles without labels. When the polyester was recycled, the recyclability was evaluated based on the presence or absence of flake biting failure and filter pressurization. Compared to the flakes without the label, the flakes with the label were evaluated as ◯ when the number of bite defects and the number of times the filter was boosted was the same or once more, and as × when the number of times was more than two times.
The following characteristics were evaluated for each of the polyester-based films listed in Table 2 below.

[Heat shrinkage rate (before heat shrinkage)]
A polyester film is cut into a square of 10 cm × 10 cm, immersed in hot water at a predetermined temperature [(90 ° C or 70 ° C) ± 0.5 ° C] for 10 seconds under no load, and then heat-shrinked, and then 25 ° C. The film was immersed in water at ± 0.5 ° C. for 10 seconds, pulled out of the water, the vertical and horizontal dimensions of the film were measured, and the heat shrinkage ratio of each was determined according to the following formula 1. The direction in which the heat shrinkage rate is large was defined as the main shrinkage direction (width direction).
Heat shrinkage rate (%) = {(length before shrinkage-length after shrinkage) / length before shrinkage} × 100 Equation 1

[Thickness spots in the width direction (before heat shrinkage)]
A wide strip-shaped film sample with a length of 40 mm in the longitudinal direction of the film and a dimension of 1.2 m in the width of the film was sampled from the film roll, and the measurement speed was 5 m / using a continuous contact thickness gauge manufactured by Micron Measuring Instruments Co., Ltd. The thickness was continuously measured in min along the width direction of the film sample (measurement length was 1 m). The maximum thickness at the time of measurement was Tmax., The minimum thickness was Tmin., And the average thickness was Tave., And the thickness unevenness in the width direction of the film was calculated according to the following formula 2.
Thickness spot (%) = {(Tmax.-Tmin.)/Tave.} × 100 Equation 2

[Maximum heat shrinkage stress in the width direction (before heat shrinkage)]
A sample of 4 mm in the longitudinal direction × 25 mm in the width direction was cut out from the polyester film, and the maximum heat shrinkage stress was measured in the stress mode using TMA SS100 manufactured by Seiko Electronics Inc. The distance between the chucks is 15 mm, the sample is attached to the probe using a dedicated chuck so that the direction between the chucks is the width direction of the film, and the interval from 30 ° C to 130 ° C is 10 ° C / min with an initial load of 40 mN. The temperature was raised. The maximum value of the obtained contraction stress was defined as the maximum contraction stress in the width direction.

[Haze (before heat shrinkage)]
The measurement was performed using a haze meter "500A" (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136. The measurement was performed twice, and the average value was calculated.

[Crystallinity (before heat shrinkage)]
The density d of a sample of about 3 mm square was measured using a calcium nitrate aqueous solution by the density gradient tube method of JIS-K-7112, and the crystallinity was measured according to the following formula 3.
Crystallinity (%) = {dc × (d-da) / (d × (dc-da)} × 100 Equation 3
dc: 1.455 g / cm ³ (density of polyethylene terephthalate perfect crystal)
da: 1.335 g / cm ³ (density of polyethylene terephthalate completely amorphous)
d: Sample density (g / cm ³ )

[Tg; glass transition point (before heat shrinkage)]
Tg was determined according to JIS-K7121-1987 using a differential scanning calorimeter (model: DSC220) manufactured by Seiko Electronics Inc. Specifically, 10 mg of the unstretched film was heated from −40 ° C. to 120 ° C. at a heating rate of 10 ° C./min, and the endothermic curve was measured. Tangent lines were drawn before and after the inflection point of the obtained endothermic curve, and the intersection was defined as the glass transition point (Tg; ° C.).

Using the polyester raw materials D to G, various polyester films shown in Table 2 were obtained.

[Example 1]
Using grass, gold, and white ink manufactured by Toyo Ink Co., Ltd., printing for labels (three-color printing) is repeatedly applied to the entire surface of the film 1 except for 20 mm from the end in the width direction of the roll, and the film is wound and printed. A film roll was made. A printing film is unwound from this roll, and an adhesive solvent composition in which 1,3-dioxolane / polyester A is mixed so as to have a weight ratio of 90/10 is applied to the inside of one end in the film width direction to have a coating width of 4. The temperature was adjusted to 300 mg / m ² in the range of ± 2 mm, and the film was continuously applied at a processing speed of 400 m / min. A label (heat shrinkage) in which the heat-shrinkable film is an annular body is bonded by folding and adhering the film on the other widthwise end portion of the film so that the overlapped portion is at the center. A label with the main shrinkage direction of the sex film as the circumferential direction) was prepared. Then, two perforations (perforations having holes having a diameter of about 1 mm arranged at intervals of about 4 mm) were formed in parallel in the longitudinal direction of the label at intervals of about 22 mm, and the label was continuously wound up.
The roll from which the heat-shrinkable label was wound was passed through a steam tunnel and heat-shrinked. The tunnel is divided into three zones, and the temperature of 1 zone / 2 zones / 3 zones is set to 60/79/81 ° C., and the total residence time of all zones is set to 28 seconds.
Table 3 shows the production conditions and the obtained characteristics of Example 1, and FIG. 1 shows the heat shrinkage rate obtained from TMA.

[Examples 2 to 7, Comparative Examples 1 to 4]
Examples 2 to 7 and Comparative Example are the same as in Example 1 except that the temperature and residence time of the film, the adhesive solvent composition, and the steam tunnel used in Example 1 are changed as shown in Table 3. 1 to 4 packages were manufactured.
Table 3 shows the production conditions of Example 1 and the obtained characteristics. For Comparative Example 1, the heat shrinkage rate obtained from TMA is shown in FIG.

The packages of Examples 1 to 7 satisfying the requirements of the present invention have a beautiful appearance with a shrinkage finish evaluation of 4 or 5, and the adhesive strength, residual shrinkage rate, melting point, and heat-resistant blocking property of the package. The recyclability also satisfied the predetermined range, which was preferable.
On the other hand, in Comparative Example 1, since the film 5 having a low heat shrinkage rate at 90 ° C. in the width direction of 26.8% was used, the peak of the residual heat shrinkage rate of the package did not appear at 120 ° C. or lower (120). The residual shrinkage rate at ° C was 0.9%), and the shrinkage finish of the package was significantly reduced (evaluation 1). Therefore, the heat-resistant blocking test and recyclability have not been evaluated.

In Comparative Example 2, since the film 7 having a thickness unevenness of 22.0% in the width direction was used, the ink of the package was not printed uniformly and many defects such as fading occurred, so that the shrinkage finish was deteriorated (the shrinkage finish was deteriorated). Evaluation 2). Further, since the film 7 uses amorphous raw materials (polyesters F and G), the melting point is as low as 173 ° C., the heat of fusion (ΔHm) is also lowered to 17 J / g, and the evaluation of heat-resistant blocking property and recyclability is " × ”

In Comparative Example 3, since the adhesive solvent was a simple substance of 1,3-dioxolane, the adhesive strength became zero (adhesion was impossible), and an annular package could not be produced. Therefore, the heat-resistant blocking test and recyclability have not been evaluated.
In Comparative Example 4, since the residual shrinkage rate after heat shrinkage was as high as 44.9%, the shrinkage finish was significantly reduced (evaluation 1).

As described above, the package of the present invention has excellent adhesive strength and shrinkage finish, and since it uses a raw material consisting substantially only of polyethylene terephthalate, it can be recycled together with a PET bottle. can. From the above, the present invention is useful as a packaging body for beverage bottles.

Claims (6)

A package having a printed portion using a heat-shrinkable polyester film as a base material, and an annular body to which both ends of the film are bonded is coated on at least a part of the outer periphery of the object to be packaged in a heat-shrinked state. The package is characterized in that the coated annular body satisfies the following requirements (1) to (3).
(1) The heat-shrinkable polyester-based film used as the base material contains 90 mol% or more of the ethylene terephthalate unit in 100 mol% of all ester units. (2) The heat-shrinkable polyester-based film used as the base material performs differential scanning. It has a melting peak in the process of raising the temperature of the calorimeter (DSC), the melting point (Tm) which is the peak temperature is 200 ° C. or higher and 280 ° C. or lower, and the melting heat amount (ΔHm) which is the peak area is 40J. / G or more and 60 J / g or less (3) The peak of the heat shrinkage rate of the heat-shrinkable polyester-based film used as the base material obtained by thermal mechanical analysis (TMA) in the circumferential direction of the packaged object is 60 ° C or more and 120 ° C or less. The heat shrinkage at the peak is 1% or more and 40% or less. The package according to claim 1, wherein the peel strength of the adhesive portion of the coated annular body is 2N / 15 mm or more and 15N / 15 mm or less. The package according to claim 1 or 2, wherein the heat-shrinkable polyester film as the base material has an intrinsic viscosity (IV) of 0.5 dL / g or more and 0.8 dL / g or less. The package according to claim 1 to 3, wherein the adhesion is made by an organic solvent composition. The package according to claim 4, wherein the organic solvent composition contains a polymer component. A packaging container comprising the package according to any one of claims 1 to 5 on at least a part of the outer periphery of the container.

Images